Surface-effect machine suitable for transoceanic traffic

ABSTRACT

A multi-cushion surface effect machine designed for use as an ocean-going air-cushion vehicle, comprises in its basic structure a flat capacity which extends above the cushion-bounding skirts and which forms a manifold for supplying a number of cushions in parallel from a common pressure fluid source by way of flowlimiting venturis, the same being disposed flat in the capacity. Below the load bearing platform of the machine are fitted three or more projecting walls which extend parallel to the machine longitudinal axis and form parallel channels, the flexible skirts bounding the fluid cushions being alined in rows as near one another as possible.

United States Patent 1191 Bertin Mar. 26, 1974 SURFACE-EFFECT MACHINE SUITABLE 3,369,623 2/1968 Bertin 180/127 FOR TRANSOCEANIC TRAFFIC 3,266,757 8/1966 Guienne 180/127 75 I ventor: ean Henri Bertin, 1 n llleumysupseine France Primary Examiner-George E. A. l-ialvosa Assistant Examiner-Sherman D. Basinger [73] Assignee: Bertin & Cil, Plaisir, France Attorney, A m, or Fi -A W. Breiner [22] Filed: Aug. 23, 1972 21 Appl. No.: 282,919 1571 ABSTRACT Related Application Dam A multi-cushion surface effect machine designed for [62] Division of Ser No 44 039 June 8 1970 Pat. Na use as an ocean-going air-cushion vehicle, comprises in its basic structure a Hat capacity which extends above the cushion-bounding skirts and which forms a manifold for supplying a number of cushions in paral- ,lel from a common pressure fluid source by way of flow-limiting venturis, the same being disposed flat in the capacity. Below the load bearing platform of the machine are fitted three or more projecting walls which extend parallel to the machine longitudinal axis and form parallel channels, the flexible skirts bounding the fluid cushions being alined in rows as near one another as possible.

5 Claims, 21 Drawing Figures L 5 141 52 ii i 50 im-1113 s 31: 1 I: 45 4 r1 g 48 44 a 1 a 44 a a 1 Q 2 PATENIEI] IIIIZS I814 SHEET 1 OF 5 PATENTEDIARZS I974 SHEET 3 UP 5 E 5 H mm Nanci. u

PATENTED "AR 26 I974 SHEET Li [1F 5 PATENIEBmzs m4 SHEET 5 OF 5 AY/ fll/ SURFACE-EFFECT MACHINE SUITABLE FOR TRANSOCEANIC TRAFFIC This is a divisional application of my co-pending application Ser. No. 44,039 filed June 8, 1970, now US. Pat. No. 3,688,724.

This invention is for improvements in or relating to ground-effect machines which are, borne by land or water with the interposition of a number of cushions containing air or some other pressure fluid.

It is an object of this invention to enable the various cushions to be supplied independently from a common pressure fluid source, a feature which, of course, helps stability and greatly reduces the space taken up by the supply facilities.

The invention accordingly comprises the combination of a substantially flat capacity which extends above the cushion-bounding curtains or walls or skirts or the like and which forms a header for supplying a number of cushions in parallel from a common pressure fluid source and which communicates with the cushions to be supplied by way of flow-limiting venturis, the same being disposed flat in the capacity. Preferably, the venturis are two-dimensional with a flat cross-section. Preferably too, the venturis are placed flat up against one of the capacity walls, such wall possibly forming one of the venturi walls.

The flat capacity contrived like a double bottom below the vehicle platform and supplying the air cushion chambers via venturis can be made rigid, and thus suitable for forming the load-bearing frame of the vehicle, if the walls of the flat capacity are interconnected at least in some places by tubes made of a rigid and strong substance such as steel. These tubes, which are closed on themselves and filled with gas or air, can be large enough to enable the vehicle to float and held to make the vehicle amphibious.

Advantageously, the tubes form the side wall of the flat capacity, interconnecting the two walls at their periphery. One or more tubes can also be disposed between the walls of the flat capacity so as to leave the air cushion supply paths therein unobstructed.

The invention also relates to the construction of a large ground-effect machine, more particularly a machine for long-distance sea travel, such as an oceangoing ground-effect machine. Of course, a machine of this kind needs a large surface to receive the air cushion pressure and thus produce the lift; unfortunately, when the transverse dimensions of skirts of this kind are increased, the forces withstood by the skirts also in crease, and so large skirts must have thick and dense walls, a disadvantageous factor.

According to a feature of the invention, a large number of skirts are used which are small in relation to the machine dimensions but which are devised and distributed to make maximum use of the machine bottom surface and which are confined in at least two passages contrived below the machine by at least three walls which extend parallel to the machine longitudinal axis.

Preferably, the skirts are of the kind comprising a top polygonally shaped securing edge, for instance, in shape substantially square or oblong so as to contain the maximum available surface, on the ceiling surface of each of the corridors whereas the free bottom edge of the skirts is in shape substantially circular. These features combine very advantageously with the flat cushion supply capacity to reduce size and improve the efflciency of the independent supply for a large number of air cushions.

The machine can also comprise means for bounding the longitudinal channels or passages at the front and- /or rear so that an extra pressure fluid cushion supplied at least by leaks from the other cushions can be formed in each such channel or passage. For instance, the confining means can be formed by those of the flexible skirts which are at the front and/or rear of the machine in the longitudinal channels or passages, the walls of such skirts being disposed very near and/or in contact with such longitudinal walls. Of course, either the other skirts can be disposed similarly or a larger gap can be left between such other skirts and the passage walls.

A machine thus devised is very stable yet can be of very large dimensions and very great weight.

The following description, taken together with the accompanying exemplary non-limitative drawings, will show clearly how the invention can be carried into effect.

In the drawings FIG. 1 is a view in vertical projection and in section of a machine for travelling over water and comprising an embodiment of the invention;

FIG. 2 is a view in horizontal projection and in section on the line II--II of FIG. 1, the line I-I of FIG. 2 denoting the trace of the section plane of FIG. 1;

FIG. 3 is a cross-section on the line III-III of FIG. 1;

FIG. 4 is a view to an enlarged scale, and in the same plane as FIG. 1, of an embodiment of a flat venturi;

FIG. 5 is a view corresponding to FIG. 4 but in horizontal projection;

FIGS. 6, 7 and 8 are sectioned views of other forms of venturi;

FIG. 9 is a view in horizontal projection of a venturi of the kind shown in FIG. 8;

FIG. 10 is a view in cross-section on the line X-X of FIG. 9;

FIGS. 11 and 12 are views in section of another form of venturi in two different operating positions;

FIG. 13 is an end view looking in the direction of an arrow F in FIG. 11;

FIG. 14 is a view in side elevation of an overland machine, but which can also float, embodied as a mixed truck;

FIG. 15 is a cross-section on the line XV-XV of FIG. 14, the view being in the direction of the arrows in FIG. 14;

FIG. 16 is a plan view in horizontal section on the line XVI-XVI of FIG. 15;

FIG. 17 is a sectioned view in elevation on the line XVIIXVII of FIG. 19 of a ground-effect machine according to the invention devised as an ocean-going craft;

FIG. 18 is a view in section on the line XVIII-XVIII of FIG. 17;

FIG. 19 is a view in section on the line XIX-XIX of FIG. 18;

FIG. 20 is a partial view to an enlarged scale and in section on the line XX-XX of FIG. 19, showing constructional details of the flexible skirts at the front of the machine; and

FIG. 21 is a partial view in section on the line XXI- XXI of FIG. 20.

FIGS. 1-3 show a ground-effect machine assumed, in the particular example concerned, to move above the surface of water. The machine has a load-carrying platform 1, below the machine are facilities for producing air cushions to liftthe machine above the water 2. The machine has an appropriate propulsion facility which, in order to simplify the drawings, is not shown and which can be one or more air screws, a turbojet or the like. In the example shown the air cushions are of the plenum-chamber" kind and are each bounded by a flexible wall or skirt 3. The example has two rows of skirts disposed symmetrically one on each side of the vertical longitudinal plane of symmetry of the machine, such plane being parallel to the plane of FIG. 1. Each row comprises four skirts i.e., four cushions.

As the drawings also show, the skirt system has around it a skirt 4 which substantially follows the periphery of platform 1 and produces around the skirts 3 an extra air cushion energised by leakages from the air cushions bounded by the skirts 3; a separate supply may also be provided for the extra air cushion.

To ensure that the skirt 4 is firm enough, its wall is formed, as can be seen in FIG. 2, in two parts each in shape resembling a large-radius circle arc, the arcs meeting at places 4a. This feature provided considerable lift with improved efficiency, pitch stabilisation, because of the lengthwise subdivision of the air cushions bounded by the skirts 3, and roll stabilization, because of the two rows of skirts 3 disposed one on either side of the longitudinal axis, provided that the skirts 3 are supplied with compressed air independently of one another so that an excessive leakage from any one skirt at any one instant of time, for instance, because such skirt is between two waves, is not transmitted to the other skirts. The skirt supply facility shown enables the supplies to the various cushions to be made independent in this way and has other advantages. The facility comprises a flat chamber or capacity 6 which is disposed below the platform 1 and formed between the platform wall and a parallel wall 7 to which the skirts 3, 4 are secured. The chamber or capacity 6, which is rendered sealing-tight in appropriate manner except for the passages extending the skirts 3 and 4 through the wall 7, forms a sort of double bottom or flat header which is connected through a line 8 to a compressed air source comprising, in the example shown, two paralleloperating air compressors 9 each disposed in a fairing 10 open to the front, so that as the machine moves air enters the fairings with the dynamic pressure due to the movement of the machine.

Each passage through which the skirts'3, 4 are supplied from the header 6 comprises a venturi tube i.e., and as can be seen in FIG. 4, a tube having a throat 11 following a convergent inlet part 12 which opens into the header 6 at a place 13. The venturis are twodimensional i.e., flat in shape and are disposed horizontally in a double bottom 6 so that the axis of each venturi is substantially parallel to the walls 1, 7. This feature enables the venturis to be of adequate axial length, a dimension which is of course fairly important for satisfactory operation of a venturi tube if a large gap cannot be left between the walls 1 and 7. The space taken up by machinery is therefore reduced; also, the platform 1 and the centre of gravity can be lowered. The arrows in FIG. 4 show the path taken by the air which enters the inlet orifice 13 of each venturi, then goes through the convergent part 12, throat 11 and divergent part 14 to reach the corresponding skirt through aperture 15 in wall 7. A blade lattice 16 helps to improve the efficiency of the bend at the venturi exit.

FIGS. 4 and 5 also show an embodiment ofa venturi formed by two parallel side plates or webs 17 which are secured to the wall 7 perpendicularly thereto by a curvilinear cylindrically surfaced metal member 18 secured hermetically to the plates 17, the generatrices of the member 18 being perpendicular to the plates 17. Each venturi is therefore bounded by the plates 17, the member 18 and the wall 7.

FIGS. 1, 2 and 3 show the flat venturi a associated with each skirt 3 andfour flat venturis b distributed over wall 7 between the skirts 3 to provide direct energization of skirt 4 in addition to the leakage air energization from skirts 3. The flat venturis can of course be embodied in many other ways.

With venturis designed so that the rate of flow at the throat in normal operation is slightly below or equal to the speed of sound, the flow through each venturi is limited automatically when the leakage flow from any skirt exceeds its normal operating value; this feature of course helps to make the skirts independent of one another.

Another way in which the flat venturis can be used to limit the rate of flow is for the venturi walls to be adapted to be moved relatively to one another to vary the constriction at the throat. A first embodiment of this kind is shown in FIG. 6 where the venturi comprises, between side members 17, two curvilinear cylindrical walls 18, 18a articulated around stationary spindles 20. The two walls 18 can be moved towards and away from one another by being pivoted around the spindles 20 by actuators 21 which can be controlled by the pressure in the corresponding cushion. In a system of this kind, of course, the venturi exit orifice cannot be directly connected to the orifice l5 communicating with the skirt to be energized, and so in this case the walls 17 can co-operate with an extra fixed wall 22 rigidly secured to the walls 17 to form a closed box to which the venturi delivers and which communicates with the aperture 15.

In the variant shown in FIG. 7, variation of throat cross-section and therefore the rate of flow, is controlled by the negative pressure produced in the throat zone in the venturi. Such negative pressure depends upon the rate of flow of the fluid, and the rate tends of course to increase with the leakage from the skirt energised. The system is similar to FIG. 6 except that the venturi walls 18, 18a are acted on by springs 23 which balance the action of the negative pressure. When the rate of flow of the fluid at the throat and the negative pressure increase, the two walls tend to move towards one another and reduce the throat crosssection.

In FIGS. 8-10 the same effect is produced by using for the venturi walls two flexible plates 18, 18a which are made of. rubber or some other resilient and stretchable substance, the plates curving towards one another to an extend varying with the strength of the negative pressure. Conveniently, and as shown in FIG. 9, the plates are circular to facilitate deformation of the rubher.

In the embodiment shown in FIGS. 11-13, the main integers are those previously described with reference to FIG. 4; in this case, however, the foil 13 which can be of sheet metal or some other material, is deformable because its free end edge 25 (the edge perpendicular to the plane of FIG. 11) has both its ends guided in slides 26 disposed in the members 17. For instance, and as can be seen in FIG. 13, edge 25 can be wound around a rod whose projecting ends 27 are guided in the slides 26. The same can be inclined to facilitate the movement of the rod ends 27. Because of the possible movements which the edge 25 can make, and provided of course that the foil or sheet 18 is not rigidly connected, at least in its intermediate part, to the members 17 but can move thereon with satisfactory sealingtightness (e.g. through the agency of a teflon-covered edge), the sheet 18 distorts to an extent varying with the negative pressure at the venturi throat and thus varies throat cross-section.

The facility described has various advantages. In addition to the advantages previously mentioned as regards space saving, since the skirts supply header can be made very flat, and as regards the reduction and substantial obviation of air leakages from any air cushions which happen to be too open to atmosphere, the machine bodywork is of improved sealing-tightness, since there is no need for a large number of ducts of relatively complicated shape to extend through the bodywork a great advantage for sea-going machines. Since the header is flat, a large number of generators of compressed air or some other pressure fluid can readily be associated with a large number of air cushions. Also, should the header bottom wall be damaged, a risk which is particularly likely in a sea-going machine, the air escapes below the vehicle so that there is a loss of stability but the general lift remains.

For buoyancy, sealed chambers can be provided, for instance, in the form of inflatable tubes disposed around platform 1.

The machine shown in FIGS. 14-16, also comprises plenum chamber air cushions each bounded by a flexible skirt 3 and can move either above land, denoted by the reference 2a, or above water, for instance, across a river or lake. In the example, two skirt rows are disposed symmetrically one on either side of the longitudinal vertical plane of symmetry of the machine, such plane being represented by the line AA in FIG. 16. Each row comprises three skirts i.e., three cushions. There is also an extra skirt at front and rear and positioned symmetrically of the line AA to leave space for wheels 32. The skirt supply facility providing independent skirt supplies from a common source is the same as hereinbefore described, the common source in this embodiment comprising an air compressor 9 driven by an e.g. electric motor 9a, Compressor 9 has fairing which is open to the front so that air is forced into the fairing by dynamic pressure as the machine moves. Each passage via which the skirts 3 are supplied from the header 6 is embodied, as described with reference to FIGS. 4 and 5, by a flat venturi placed horizontally in the capacity 6. The two horizontal walls 1, 7 thereof are interconnected by tubes 30 which are closed on themselves hermetically and filled with a gas, for instance, air; the tubes 30 are large enough to give the machine buoyancy in the water even if the air cushions do not operate; the capacity 6 cannot provide buoyancy, for when the air cushions are not in operation air can enter the capacity 6 via the venturis. The tubes 30 are made of steel or some other strong metal and are rigidly secured, e.g. by welding or in some other way, to the two walls 1, 7 and thus help to stiffen the system which the tubes 30 form in co-operation with the walls 1, 7, such system then being suitable on its own to form a vehicle frame or chassis to which arms 33 bearing the wheels 32 can be secured in any appropriate manner.

In the embodiment shown, a single tube 30 extends over the whole periphery of the capacity 6 and is embodied by welded-together sections. The tube 30 therefore forms the sealing side wall between the two horizontal walls 1, 7. Since the air from the compressor 9 to the various venturis takes a longitudinal path, another tube 31 can be placed on the longitudinal axis of capacity 6 between the two skirt rows. If there are more than two skirt rows, a further tube parallel to the longitudinal axis can be provided. The tube 31 can be independent of the peripheral tubes 30; in the example shown, the tube 31 is connected to the tubes 30, eg by welding. The extra front skirt is supplied through a venturi placed horizontally in a small flat capacity 6a bounded laterally by a tube 30a. The compressor output is branched at a place 8a to supply the capacity 6a. The embodiment could of course be modified. More particularly, the tubes 30 could extend over only some of the periphery of the chambers 6, the remainder thereof being closed hermetically by any sort of side wall. Similarly, connecting means in addition to the tubes 30 and 31 could be provided between the walls 1 and 7.

Referring to FIGS. 17-21, a ground-effect machine is moving, in the direction indicated by an arrow F, along a bearing surface 2 which is water in this particular example, the machine being an ocean-going groundeffect machine. The machine structure 40 comprises a base member 1a which is hollow and sealing-tight to form a buoyancy reserve, and an operative part 41 which is connected to the base member 1a with partitioning such that the structure 40 forms a very rigid hollow member. Stiffeners 42 increase the stiffness of member 1a. Inflatable chambers 43 disposed along and on each side of the machine protect the same and increase buoyancy. Members made of an expanded plastics material can be used instead of the chambers 43.

Rigid walls 44 which have a thin bottom edge and which are disposed lengthwise of the machine project below base member la towards surface 2 and thus bound longitudinal channels or passages. In the embodiment described, there are four walls 44 bounding three such channels or passages. Disposed in each channel is a wall 7 which is substantially parallel to base member la and which co-operates with the associated walls 44 and the member 1a to bound a flat capacity 6 supplied with pressure fluid. Secured to each wall 7 are flexible skirts 3 each bounding a pressure fluid cushion 3a of the plenum chamber kind and extending between two walls 44 to near the surface 2. Advantageously, the skirts 3 have in plan near the wall 7 a poly gonal shape which is substantially square in this embodiment (as represented by thin chain-dotted lines 3b in FIGS. 19 and 21) while their shape at their free edge near the surface 2 is substantially circular. Preferably, the polygonal surface is greater than the circular surface so that the pressure fluid contained by the skirts ensures vertical stability thereof. Skirts of this kind have already been disclosed in US. Pat. Nos. 3,369,623 and 3,414,075. Their advantage is that they make optimum use of the surface of the walls 7 for lift. Another possibility is to have skirts which are in plan near the wall 7 oblong-shaped and near the bearing surface substantially circular.

The cushions 3a bounded by the various skirts are supplied independently of one another by the corresponding capacity 6 via a two-dimensional convergentdivergent nozzle a in the form of a flat venturi. The capacities 6 are supplied from two fans or blowers 45 driven by motors 46, with dynamic intakes 47 for external fluid, the intakes 47 being disposed e.g. at the front of the machine. Each fan is associated with a lateral capacity 6 and supplies the same through a duct 48. The central capacity 6 is supplied through offshoots 480 from the ducts 48 and disposed in the base member la. Since they are separated from one another by the walls 44, the capacities 6 could also be supplied independently e.g. by means of three separate fans.

Advantageously, the longitudinal channels or passages bounded by the walls 44 are closed at their front and rear ends so as to bound the supplementary pressure-fluid cushions supplied by leakages from the cushions 3a bounded by the skirts 3. Accordingly, the skirts 3 at the front and/or rear of the longitudinal channels or passages bounded by the walls 44 have walls which are disposed very near the longitudinal walls 44, as can be seen in FIGS. and 21. It would also be possible for the walls described as being very near the longitudinal walls 44 to be in contact therewith. Each longitudinal channel therefore bounds a pressure fluid cushion which is independent of the other cushions bounded by the other channels, so that the machine has very good lateral stability. Depending upon the conditions in which the machine is used, the free bottom edge of the skirts 3 can be substantially at the same level as the free edge of the walls 44, as shown in the figures, or higher or lower.

Any form of propulsion can be used. In the example shown, propulsion is by four screws 49 which are, with advantage, disposed in fairings and which are placed at the front and' rear of the machine respectively; the screws 49 are driven by motors 50 and can each make an appropriate angle with the machine axis so as not to cause disturbing interactions. The machine also has two fins 51 positioned, if required, outside the air stream produced by the screws 49.

The operative part of the machine comprises a central freight compartment 52 and, on either side thereof, engine compartments 53 and passengers compartments The interior of each skirt communicates with the flat capacity 6 above it, and receiving the compressed air from the fans 45, via a venturi tube of the kind previously described with reference to FIGS. 4 and 5. The space required for the equipment of the machine is therefore reduced, and the base member la and the centre of gravity can be lower than previously.

The ground-effect machine according to the invention is very stable yet can be very large. For instance, the skirts 3 can readily be 20 metres in diameter, and the number of longitudinal channels in which the skirts 3 are disposed can be increased by increasing the number of walls 44. With skirts of this size and using three or four longitudinal channels, machines weighing from 1,600 to 3,000 tons can be constructed.

The invention is not of course limited to the embodiments described and covers embodiments arising from the use of equivalent technical means.

The walls 44 can be hollowed so as not to increase weight excessively and can be made ofa rigid or slightly deformable material.

The means for bounding the longitudinal channels at the front and/or rear of the machine can differ from those described; for instance, a flexible wall which in plan preferably resembles a portion of circle arc can be used for each channel or passage.

I claim:

1. In a surface effect machine having a load-carrying platform movable in the direction of its longitudinal axis over a bearing surface with the interposition of pressure fluid cushions between said platform and said surface, and a plurality of laterally-spaced and longitudinally-extending keel-like walls projecting downwardly from said platform towards said surface and forming the sidewalls of channels extending longitudinally and spaced laterally under said platform, the improvement comprising a partition plate extending between the sidewalls of each of said channels in spaced relation with said platform to subdivide the respective channel into a vertically-minor longitudinallyextending upper compartment and a vertically-major longitudinally-extending lower compartment, a plurality of flexible skirts depending from each partition plate and aligned behind each other in each lower compartment, separate and individual passage means extending through each partition plate for connecting each skirtbounded space with its overtopping upper compartment, and means for supplying each upper compartment with pressure fluid, whereby each upper compartment acts as a pressure-fluid supply manifold for the underlying skirt-bounded spaces wherein said cushions are formed.

2. A machine as claimed in claim 1, wherein said passage means comprise a succession of venturi-shaped scoops projecting into and extending generally horizontally in each of said upper compartments to tap pressure fluid therefrom and discharge said pressure fluid into respective underlying skirt-bounded spaces, each of said venturi-shaped scoops being generally bidimensional and having a generally horizontal major dimension and a generally vertical minor dimension.

3. A machine as claimed in claim 1, wherein said flexible skirts have an attached upper end at said partition plates and a free lower end remote therefrom, said free end being of substantially circular shape whereas said attached end is of a shape which differs from a circle, the transverse size of said end being substantially equal to the transverse width of the respective partition plate whereby said attached end extends across substantially the whole width of the respective channel, the attached ends of the skirts alined in the same channel being substantially contiguous to each other.

4. A machine as claimed in claim 3, wherein said attached end is of generally polygonal shape.

5. A machine as claimed in claim 4, wherein said attached end is of generally square shape.

I! 4 l Il PRINTERS TRIM L nu-Moms, I

UNITEI-I STATES 'VPATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 799, 095

Dated March 26, 1974 l f Jean Henri BERTIN It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Title page, in the heading, [73] Assignee, Bertin & Cil" should read Bertin & Cie Title page, in the heading, the priority claim should appear as follows:

-- Priority is claimed of 1 French application for Patent No. 69. 19183 filed June 10, 1969; French application for patent of Addition No. 69. 19184 filed June 10, 1969; and 6 French application for patent of Addition No. 69.19185 filed June 10, 1969 Column 4, line 60, "extend" should read extent Signed and sealed this 12th day of November 974.

(SEAL) AtteSt:

C. MARSHALL DANN Commissioner of Patents MCCOY M. GIBSON JR. Attesting Officer FORM PO-1050 (10-69) USCOMM-DC GOS'IG-F'GD 9 Hi5. GOVERNMENT PRINTING OFFICE "l9 0-366-331, 

1. In a surface effect machine having a load-carrying platform movable in the direction of its longitudinal axis over a bearing surface with the interposition of pressure fluid cushions between said platform and said surface, and a plurality of laterallyspaced and longitudinally-extending keel-like walls projecting downwardly from said platform towards said surface and forming the sidewalls of channels extending longitudinally and spaced laterally under said platform, the improvement comprising a partition plate extending between the sidewalls of each of said channels in spaced relation with said platform to subdivide the respective channel into a vertically-minor longitudinallyextending upper compartment and a vertically-major longitudinally-extending lower compartment, a plurality of flexible skirts depending from each partition plate and aligned behind each other in each lower compartment, separate and individual passage means extending through each partition plate for connecting each skirt-bounded space with its overtopping upper compartment, and means for supplying each upper compartment with pressure fluid, whereby each upper compartment acts as a pressure-fluid supply manifold for the underlying skirt-bounded spaces wherein said cushions are formed.
 2. A machine as claimed in claim 1, wherein said passage means comprise a succession of venturi-shaped scoops projecting into and extending generally horizontally in each of said upper compartments to tap pressure fluid therefrom and discharge said pressure fluid into respective underlying skirt-bounded spaces, each of said venturi-shaped scoops being generally bi-dimensional and having a generally horizontal major dimension and a generally vertical minor dimension.
 3. A machine as claimed in claim 1, wherein said flexible skirts have an attached upper end at said partition plates and a free lower end remote therefrom, said free end being of substantially circular shape whereas said attached end is of a shape which differs from a circle, the transverse size of said end being substantially equal to the transverse width of the respective partition plate whereby said attached end extends across substantially the whole width of the respective channel, the attached ends of the skirts alined in the same channel being substantially contiguous to each other.
 4. A machine As claimed in claim 3, wherein said attached end is of generally polygonal shape.
 5. A machine as claimed in claim 4, wherein said attached end is of generally square shape. 